Energy efficient network communication device and method

ABSTRACT

The present invention discloses an energy efficient network communication device comprising: a media-access-controller for outputting a transmission-end low power idle (LPI) indication and receiving a reception-end LPI indication; a media-independent-interface for generating a transmission-end LPI signal according to the transmission-end LPI indication, and generating the reception-end LPI indication according to a reception-end LPI signal; and a physical-layer-circuit, coupled to several pairs of transmission lines, for converting the transmission-end LPI signal into a transmission signal to send it to a reception end for requesting an LPI mode and receiving a reception signal from the reception end to convert it into the reception-end LPI signal. Said physical-layer-circuit uses some of the several pairs of transmission lines for transmission and reception when keeping the other pairs of transmission lines unused to save power; furthermore, the physical-layer-circuit can enter the LPI mode from an idle mode for additional power saving.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a network communication device and anetwork communication method, especially to a network communicationdevice and a network communication method capable of power saving.

2. Description of Related Art

In the prior art, after a network connection is established, atraditional network device (e.g. an Ethernet network device incompliance with 1000BASE-T standard) has to send an idle pattern to areception end continually to thereby keep the connection alive even ifthe network device is in an idle state with no need to do transmissionor reception. Unfortunately, although the idle state is applied, thepower consumption of the traditional network device is merely a bit lessthan that in a normal state. Therefore, in order to save more power,IEEE works out Energy Efficient Ethernet (EEE) standard which allows anetwork device to enter a low power idle (LPI) mode from theaforementioned idle sate to turn off the operation of a physical layercircuit in the network device under the LPI mode. In the meantime, EEEstandard also requires that the network device must come back from theLPI mode to the normal state immediately to process data once atransmission or reception request occurs.

Generally speaking, an Ethernet network device conforming to 1000 BASE-Tstandard utilizes four pairs of wires to carry out full-duplextransmission. However, a (U.S. Pat. No. 7,835,389B2) provides aframework in compliance with 100 BASE-T standard for performingtransmission by only one pair or two pairs of wires. This framework hasa data transmission rate higher than that of a traditional deviceconforming to 1000 BASE-X standard, but it also brings much circuitcomplication and power consumption issues; moreover, this framework cannot support EEE standard, which means that it can not enter the LPI modeto cut the operation of the physical layer circuit for power saving.

SUMMARY OF THE INVENTION

In consideration of the deficits of the prior art, a purpose of thepresent invention is to provide an energy efficient networkcommunication device and an energy efficient network communicationmethod for making an improvement.

Another purpose of the present invention is to provide an energyefficient network communication device and an energy efficient networkcommunication method for merely using partial transmission lines tocarry out transmission and reception when keeping the other transmissionlines unused, so as to accomplish an energy efficient function.

The present invention discloses an energy efficient networkcommunication device. According to an embodiment of the presentinvention, the energy efficient network communication device comprises:a media access controller for outputting a transmission-end low poweridle indication (TX-LPI indication) and receiving a reception-end lowpower idle indication (RX-LPI indication); a media independent interfaceincluding a media independent transmission interface and a mediaindependent reception interface in which the media independenttransmission interface is for generating a transmission-end low poweridle signal (TX-LPI signal) according to the TX-LPI indication while themedia independent reception interface is for generating the RX-LPIindication according to a reception-end low power idle signal (RX-LPIsignal); and a physical layer circuit, electrically coupled to the mediaindependent interface and several pairs of transmission lines, includinga physical layer transmission circuit and a physical layer receptioncircuit in which the physical layer transmission circuit is coupled tothe media independent transmission interface for converting the TX-LPIsignal into a transmission signal and sending the transmission signal toa reception end to thereby ask the reception end to enter a low poweridle mode (LPI mode) while the physical layer reception circuit iscoupled to the media independent reception interface for receiving areception signal from the reception end and converting the receptionsignal into the RX-LPI signal, wherein the physical layer circuit usesat least one of the several pairs of transmission lines for sending thetransmission signal and receiving the reception signal, and keeps atleast another one of the several pairs of transmission lines unused, andafter sending the transmission signal and/or receiving the RX-LPIsignal, the physical layer circuit enters the LPI mode from an idle modeand stops the operation of some or all of the physical layer circuit toreduce power consumption.

The present invention also discloses an energy efficient networkcommunication method which could be carried out by an energy efficientnetwork communication device. According to an embodiment of the presentinvention, the energy efficient network communication method comprisesthe following steps: entering an idle mode from a normal mode;generating a transmission-end lower power idle indication (TX-LPIindication); generating a transmission-end lower power idle signal(TX-LPI signal) according to the TX-LPI indication; converting theTX-LPI signal into a transmission signal; using at least one of severalpairs of transmission lines to output the transmission signal to areception end for asking the reception end to enter a lower power idlemode (LPI mode), and keeping at least another one of the several pairsof transmission lines unused; using the at least one of the severalpairs of transmission lines to receive a reception signal from thereception end, and keeping the at least another one of the several pairsof transmission lines unused; converting the reception signal into areception-end low power idle signal (RX-LPI signal); and afteroutputting the transmission signal and/or receiving the RX-LPI signal,entering the LPI mode from the idle mode for reducing power consumption,wherein the power consumption under the normal mode is higher than thepower consumption under the idle mode while the power consumption underthe idle mode is higher than the power consumption under the LPI mode.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiments that areillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the energy efficient networkcommunication device of the present invention.

FIG. 2 illustrates an embodiment of the media access controller of FIG.1.

FIG. 3 illustrates an embodiment of the physical layer circuit of FIG.1.

FIG. 4a and FIG. 4b illustrate an embodiment of the decryption circuitof FIG. 3.

FIG. 5 illustrates an embodiment of the operation procedure of thedecryption circuit of FIGS. 4a and 4 b.

FIG. 6 illustrates an embodiment of the transmission and receptioncircuits of FIG. 3.

FIG. 7a and FIG. 7b illustrate an embodiment of the operation procedureof the physical layer circuit of FIG. 3.

FIG. 8 illustrates an embodiment of the energy efficient networkcommunication method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description uses language by referring to terms of thefiled of this invention. If any term is defined in the specification,such term should be explained accordingly. Besides, the connectionbetween objects or events in the disclosed embodiments can be direct orindirect provided that these embodiments are still applicable under suchconnection. The mentioned “indirect” means that an intermediate objector a physical space is existed between the objects, or an intermediateevent or a time interval is existed between the events. In addition, thefollowing description relates to network communication, and thus theknown detail in this filed will be omitted if such detail has little todo with the features of the present invention. Furthermore, the shape,size, and ratio of any element and the step sequence of any flow chartin the disclosed figures are just exemplary for understanding, not forlimiting the scope of this invention.

Besides, each embodiment in the following description includes one ormore features; however, this doesn't mean that one carrying out thepresent invention should make use of all the features of one embodimentat the same time, or should only carry out different embodimentsseparately. In other words, if an implementation derived from one ormore of the embodiments is applicable, a person of ordinary skill in theart can selectively make use of some or all of the features in oneembodiment or selectively make use of the combination of some or allfeatures in several embodiments to have the implementation come true, soas to increase the flexibility of carrying out the present invention.

The present invention discloses an energy efficient networkcommunication device and an energy efficient network communicationmethod. The energy efficient network communication device and method arecapable of transmitting and receiving data with a part of several pairsof transmission lines while the other part of the several pairs oftransmission lines remains unused; furthermore, the device and methodcan enter a low power idle (LPI) mode for power saving. In the followingembodiments, the network communication device and method support orcomply with IEEE Ethernet network standards (i.e. 802.3 standardseries), and support or conform to energy efficient Ethernet (EEE)standard. Provided that an implementation is applicable, people ofordinary skill in the art can choose components or steps equivalent tothose described in this specification to realize the present invention,which means that the scope of this invention is not limited to theembodiments in the specification. Besides, since some or all elements ofthe network communication device of the present invention could beknown; therefore, detail of such elements will be omitted provided thatthe omission nowhere dissatisfies the specification and enablementrequirements. On the other hand, the network communication method can becarried out by the network communication device of this invention or theequivalent device thereof; likewise the following description willabridge the hardware details or well-known parts of the method providedthat the disclosure still satisfies the specification and enablementrequirements.

Please refer to FIG. 1 which illustrates an embodiment of the energyefficient network communication device of the present invention. Thisembodiment could be an Ethernet network communication device such as theEthernet network communication device conforming to or supporting 1000BASE-T (IEEE 802.3ab) standard, and is able to comply with or supportthe standard or concept of energy efficient Ethernet (EEE). As shown inFIG. 1, the energy efficient network communication device 100 of thisembodiment comprises: a media access controller (MAC) 110 for outputtinga transmission-end low power idle indication (TX-LPI indication) andreceiving a reception-end low power idle indication (RX-LPI indication);a media independent interface (MII) 120, coupled to the MAC 110,including a media independent transmission interface (MII TX) 122 and amedia independent reception interface (MII RX) 124 in which the mediaindependent transmission interface 122 is for generating atransmission-end low power idle signal (TX-LPI signal) according to theTX-LPI indication while the media independent reception interface 124 isfor generating the RX-LPI indication according to a reception-end lowpower idle signal (RX-LPI signal); and a physical layer circuit (PHY),electrically coupled to the media independent interface 120 and severalpairs of transmission lines 140 (e.g. the Cat-5, Cat-5e, Cat-6 or Cat-7twisted pair cable). An embodiment of the several pairs of transmissionlines 140 includes a first pair of transmission lines 142, a second pairof transmission lines 144, a third pair of transmission lines 146 and afourth pair of transmission lines 148; meanwhile, the physical layercircuit 130 includes a physical layer transmission circuit (PHY TX) 132and a physical layer reception circuit (PHY RX) 134 in which thephysical layer transmission circuit 132 is coupled to the aforementionedmedia independent transmission interface 122 for converting the TX-LPIsignal into a transmission signal (e.g. a pulse amplitude modulation(PAM) signal) and sending the transmission signal to a reception end 150through at least one of the several pairs of transmission lines 140(e.g. the first pair of transmission lines 142 and/or the second pair oftransmission lines 144), so as to ask the reception end 150 to enter alow power idle mode (LPI mode); on the other side, the physical layerreception circuit 134 is coupled to the aforementioned media independentreception interface 124 for receiving a reception signal from thereception end 150 through the mentioned at least one pair oftransmission lines (i.e. the first pair and/or the second pair oftransmission lines 142, 144) and converting the reception signal intothe RX-LPI signal. The above-mentioned physical layer circuit 130 notonly uses the at least one pair of transmission lines to executetransmission and reception, but also keeps at least another pair of theseveral pairs of transmission lines 140 (e.g. the aforementioned thirdpair of transmission lines 146 and/or the fourth pair of transmissionlines 148) unused, so as to reduce power consumption. Additionally,after outputting the transmission signal derived from the TX-LPIindication and/or receiving the RX-LPI signal, the physical layercircuit 130 will enter the LPI mode from an idle mode and stop theoperation of at least some of its own circuits for more power saving.

In accordance with the above description, when the physical layercircuit 130 uses two pairs of transmission lines for transmission andreception, the symbol rate thereof will be less than that of thecondition using only one pair of transmission lines. For example, if thenetwork communication device 100 of the present invention uses two pairsof transmission lines for transmission at the rate of 100 Mb/s per pair(that is to say the total rate equal to 200 Mb/s) while the physicallayer circuit 130 converts the signal from the media independenttransmission interface 122 into two sets of transmission signals TA, TBin a 3-bits format for output (which means that the two sets oftransmission signals TA, TB are delivered by the two pairs oftransmission lines respectively), the corresponding symbol rate per pairis {2×100 (Mb/s)}/{2×3 (bit)}=33.3 Mhz; however, if the networkcommunication device 100 merely uses one pair of transmission lines fortransmission at the same total rate 200 Mb/s (which means that alltransmission signal is delivered by the only one pair of transmissionlines), the corresponding symbol rate per pair will be {2×100 (Mb/s)}/{3(bit)}=66.6 Mhz. Please note that before the network communicationdevice 100 of this embodiment issues the LPI indication, it enters anidle mode from a normal mode first; thereafter, it sends the LPIindication and enters the LPI mode for power saving. The powerconsumption of the network communication device 100 is relativelyhighest under the normal mode, second highest under the idle mode, andlowest under the LPI mode; in other words, the power consumption of thenormal mode is higher than that of the idle mode while the powerconsumption of the idle mode is higher than that of the LPI mode,wherein the normal mode and the idle mode support or conform to IEEEEthernet network standards (i.e. 802.3 standards).

Please refer to FIG. 1 and the above description. In the presentembodiment, the media access controller 110 includes a media accesscontrol circuit (e.g. a media access control circuit supporting or incompliance with EEE (IEEE 802.3az) standard) for issuing theaforementioned TX-LPI indication, so as to ask the reception end 150 toenter the LPI mode. The media access control circuit can also receivethe RX-LPI indication, and thereby determines whether to enter the LPImode to shut down the operation of at least some circuits for powersaving. However, in another embodiment of the present invention, themedia access control circuit (e.g. a media access control circuit incompliance with 100 BASE-T (IEEE 802.3i) standard, but not in compliancewith EEE standard) of the media access controller 110 is not capable ofissuing the TX-LPI indication; in this case, the media access controller110 of this invention will be configured with a transmission bufferwhich is coupled between the media access control circuit and theaforementioned media independent transmission interface 122 foroutputting the TX-LPI indication according to a buffer capacitythreshold after the media access control circuit stops sending packets.In other words, if the media access control circuit stops sendingpackets while the capacity of the transmission buffer reaches thementioned buffer capacity threshold (which means that the transmissionbuffer is going to finish or has finished sending packets), thetransmission buffer can then ask the reception end 150 to enter the LPImode by issuing the TX-LPI indication. Please note that theaforementioned media access control circuit conforming to 100 BASE-T canreceive the RX-LPI indication but can not or does not recognize theRX-LPI indication, which means that no power saving function will beexecuted by that indication. Besides, please refer to FIG. 2. Anembodiment of the transmission buffer 114 includes: a storage unit 210,coupled to the media access control circuit 112, for storingdelivery-awaited packets; a buffer capacity monitoring unit (BufferMonitor) 220 for watching the capacity of the storage unit 210 accordingto the mentioned buffer capacity threshold, and outputting anotification signal if the capacity of the storage unit 210 reaches thebuffer capacity threshold; and a low power idle indication generationunit (LPI indication generation unit) 230 for sending the TX-LPIindication according to the notification signal. More detail of thetransmission buffer 114 could be found in the disclosure of Applicant'sTaiwan patent application (Appl. Number: 098101499).

Please refer to FIG. 1 and the above description again. In the presentembodiment, the signal outputted or received by the media independentinterface 120 includes a plurality of bits. When the outputted bits havea set of predetermined values, they represent the aforementioned TX-LPIsignal; when the received bits correspond to a set of preset values,they represent the RX-LPI signal. More specifically, the TX-LPI signalof this embodiment includes a first transmission bit (e.g. atransmission enablement bit, TX_EN), a second transmission bit (e.g. atransmission error bit, TX_ER) and a third transmission bit (e.g. atransmission data bit, TXD[3:0]). If the first, second and thirdtransmission bits sequentially have a first predetermined value (e.g.0), a second predetermined value (e.g. 1) and a third predeterminedvalue (e.g. a hexadecimal value 0×1), they consequently act the TX-LPIsignal. On the other hand, the RX-LPI signal includes a first receptionbit (e.g. a reception data valid bit, RX_DV), a second reception bit(e.g. a reception error bit, RX_ER) and a third reception bit (e.g. areception data bit, RXD[3:0]); if the first, second and third receptionbits sequentially correspond to a first preset value (e.g. 0), a secondpreset value (e.g. 1) and a third preset value (e.g. a hexadecimal value0×1), they consequently act the RX-LPI signal. Please note that in orderto allow the transmission end and the reception end to recognize signalsfrom each other, the first predetermined value is equal to the firstpreset value, the second predetermined value is equal to the secondpreset value, and the third predetermined value is equal to the thirdpreset value. Please also note that the above description is forunderstanding, not for limiting the scope of the present invention.People of ordinary skill in the art can utilize an unused combination ofbit values to represent the TX-LPI signal and/or the RX-LPI signal forcarrying out the present invention according to the disclosure in thisspecification. In another word, the implementation scope of thisinvention embraces similar and equivalent modifications.

FIG. 3 illustrates an embodiment of the physical layer circuit 130 inFIG. 1. Please refer to FIG. 3 and the description in re FIG. 1. Thephysical layer transmission circuit 132 includes: a transmission-bitconversion circuit (TX-bit convertor) 310, coupled to the mediaindependent transmission interface 122, for generating atransmission-bit conversion signal according to the TX-LPI signal inwhich the bit number (e.g. 4 bits) of the TX-LPI signal is not equal tothe bit number (e.g. 3 bits) of the transmission-bit conversion signal.The physical layer transmission circuit 132 also includes: an encryptioncircuit 320 (e.g. a scrambling circuit), coupled to the transmission-bitconversion circuit 310, for generating a transmission-end encryptionsignal according to the transmission-bit conversion signal. Morespecifically, the encryption circuit 320 processes the transmission-bitconversion signal according to an encryption rule to thereby generate aplurality of transmission-end encryption bits which constitute thetransmission-end encryption signal, wherein at least some of thetransmission-end encryption bits go through a logic operation (e.g. anExclusive-OR operation) to carry the information of the TX-LPI signal.For example, the plurality of transmission-end encryption bits includesa first transmission-end encryption bit (Sdn[0]), a secondtransmission-end encryption bit (Sdn[1]) and a third transmission-endencryption bit (Sdn[2]) to convey different information respectively inwhich the first transmission-end encryption bit is for conveying theinformation of the TX-LPI signal, the second transmission-end encryptionbit is for conveying the information of a transmission-endupdate-completion indication (loc_update_done), and the thirdtransmission-end encryption bit is for conveying the information of atransmission-end reception status (loc_rcvr_status). The physical layertransmission circuit 132 further includes: a transmission circuit (TXcircuit) 330, electrically connected to the aforementioned several pairsof transmission lines 140, for generating the transmission signalaccording to the transmission-end encryption signal. Besides, once thephysical layer circuit 130 enters the LPI mode, if the media accesscontroller 110 is going to send packets, it can send a low power idlestop indication (LPI stop indication such as an indication other thanthe TX-LPI indication) to the physical layer circuit 130 through themedia independent transmission interface 122; afterwards, the physicallayer circuit 130 sends a wake-up signal to the reception end 150 inaccordance with the LPI stop indication, so as to ask the reception end150 to leave the LPI mode. The physical layer circuit 130 itself quitsthe LPI mode after receiving the LPI stop indication from the mediaaccess controller 110 and/or receiving a signal from the reception end150 asking for leaving the LPI mode (i.e. stopping requesting to enterthe LPI mode). Please note that if the media access controller 110utilizes the transmission buffer 114 of FIG. 2 for issuing the TX-LPIsignal, provided that the physical layer circuit 130 has entered the LPImode, the transmission buffer 114 will take charge of sending the LPIstop indication to the physical layer circuit 130 through the mediaindependent transmission interface 122 according to the aforementionedbuffer capacity threshold after the media access control circuit 112transmits packets again, which makes the physical layer circuit 130 sendthe wake-up signal to the reception end in light of the LPI stopindication to thereby ask the reception end 150 to leave the LPI mode.

On the other side, the physical layer reception circuit 134 of FIG. 3includes: a reception circuit (RX circuit) 340, electrically connectedto the several pairs of transmission lines 140, for generating areception-end encryption signal according to the reception signal fromthe reception end 150. In this embodiment, the reception signal is twosets of reception signals RA, RB in a 3-bits format delivered throughtwo pairs of transmission lines 140. The physical layer receptioncircuit 134 also includes: a decryption circuit 350 (e.g. a descramblingcircuit), coupled to the reception circuit 340, for generating areception-bit conversion signal according to the reception-endencryption signal. To be more specific, the decryption circuit 350processes the reception-end encryption signal composed of a plurality ofreception-end encryption bits according to a decryption rule(corresponding to an encryption rule of the reception end 150) tothereby generate the reception-bit conversion signal; furthermore, thedecryption circuit 350 performs a comparison operation to at least someof the reception-end encryption bits to verify whether theabove-mentioned decryption rule and encryption rule correspond to eachother correctly and check whether the at least some of the reception-endencryption bits carries the information of the RX-LPI signal from thereception end 150. For instance, the plurality of reception-endencryption bits includes a first reception-end encryption bit (Sdn[0]),a second reception-end encryption bit (Sdn[1]) and a third reception-endencryption bit (Sdn[2]). The decryption circuit 350 compares the firstreception-end encryption bit (Sdn[0]) with a first preset bit (Scrn[0])to determine whether the decryption rule of the local end correctlycorresponds to the encryption rule of the far end; moreover, thedecryption circuit 350 compares a logic operation result (e.g. aninversion operation result obtained by performing an inversion operationto the first reception-end encryption bit) with a first presetoperation-bit (Scr2n[0]) to determine whether the first reception-endencryption bit carries the information of the RX-LPI signal. In short,the decryption circuit 350 determines whether the local end is capableof correctly decrypting the signal from the far end and whether the farend asks for entering or leaving the LPI mode according to the resultsof comparison. The physical layer reception circuit 134 further includesa reception-bit conversion circuit (RX-bit convertor) 360, coupled tothe decryption circuit 350 and the media independent reception interface120, for generating the RX-LPI signal in accordance with thereception-bit conversion signal in which the bit number of the RX-LPIsignal (e.g. 4 bits) is different from the bit number of thereception-bit conversion signal (e.g. 3 bits). Please note that in orderto accelerate the connection establishment between the transmission endand reception end, the aforementioned decryption rule and encryptionrule are therefore built-in; however, during establishing theconnection, the two ends still need to confirm that the decryptionsequence adopted by one end in compliance with the decryption rule issynchronous with the encryption sequence adopted by the other end incompliance with the encryption rule, so as to accurately receive thesignal from the other side after the synchronization is verified andlocked. After that, the connection is formally in effect, and the localend may send the TX-LPI signal or verify the RX-LPI signal from thereception end. The establishment of the above-mentioned connection andthe synchronization verification of the decryption sequence will befurther explained in the following description.

Please refer to FIG. 4a and FIG. 4b which illustrate an embodiment ofthe decryption circuit 350 of FIG. 3. As shown in FIG. 4a and FIG. 4b ,the decryption circuit 350 includes: a first decryption sequencegeneration circuit 410 to establish the synchronization between theencryption sequence of the far end and the decryption sequence of thelocal end according to the first reception-end encryption bit (Sdn[0]),and stop using the first reception-end decryption bit (Sdn[0]) accordingto the level change (e.g. from level 0 to level 1) of a decryptionstatus signal (scr_status) to thereby use a first decryption sequence(Scrn[0], Scrn[1] . . . Scrn[k] . . . Scrn[m−1], Scrn[m]) instead as thebasis of generating the aforementioned reception-bit conversion signal,wherein the first decryption sequence is self-generated internally, andthe first reception-end encryption bit (Sdn[0]) is generated by decodingthe aforementioned reception signal according to a predetermineddecoding rule. For example, if the level of the reception signal RA is0, the first reception-end encryption bit (Sdn[0]) will be 1; if thelevel of the reception signal RA is not 0 (e.g. 1 or −1), the firstreception-end encryption bit will be 0. Besides, the decryption circuit350 also includes: a first decryption verification circuit 420 forgenerating a decryption verification signal (scr_check) according to thefirst reception-end encryption bit (Sdn[0]) and the aforementioned firstpreset bit (Scrn[0]). More specifically, if the first reception-enddecryption bit (Sdn[0]) remains the same as the first preset bit(Scrn[0]) for a certain amount or time, the decryption verificationsignal (scr_check) then indicates that the synchronization is correct bychanging its level (e.g. from level 0 to level 1), else the decryptionverification signal (scr_check) indicates that the synchronization isincorrect; in the later case, the first decryption sequence generationcircuit 410 will rebuild the synchronization according to the decryptionstatus signal (scr_status). The decryption circuit 350 further includes:a second decryption verification circuit 430 for determining the levelof the decryption verification signal (scr_check) according to thereversed first reception-end encryption bit (˜Sdn[0]) and a first presetoperation-bit (Scr2n[0]) after the synchronization is verified, so as totell whether the synchronization remains correct or not, wherein thereversed bit could be generated by an inverter 440. To be more specific,because the reception end in a distant place may output the reversedfirst reception-end encryption bit (˜Sdn[0]) to ask for the LPI modeafter the synchronization is well-established, thus the embodimentshould not only use the first decryption verification circuit 420 tocompare the first reception-end encryption bit (Sdn[0]) with the firstpreset bit (Scrn[0]), but also use the second decryption verificationcircuit 430 to compare the reversed first reception-end encryption bit(˜Sdn[0]) with the first preset operation-bit (Scr2n[0]). If any of thedecryption verification signals (scr_check) from the decryptionverification circuits 420, 430 through a logic OR gate 450 correspondsto a preset level (e.g. level 1), it means that the aforementionedsynchronization remains correct. However, if both of the decryptionverification signals (scr_check) from the two verification circuits 420,430 fail to correspond the preset level while the fore-mentionedphysical layer circuit 130 stays in a condition other than the LPI mode,it means that the synchronization has failed; in the mean time, theaforementioned decryption status signal (scr_status) will change itslevel and thereby control the first decryption sequence generationcircuit 410 to rebuild the synchronization. Additionally, the decryptioncircuit 350 includes: a second decryption sequence generation circuit460 to check the synchronization according to the reversed firstreception-end encryption bit (˜Sdn[0]) for the LPI mode after thesynchronization is established. If the synchronization is verified, thesecond decryption sequence generation circuit 460 stops using thereversed first reception-end encryption bit (˜Sdn[0]) according to thelevel change of the decryption status signal (scr_status), and uses asecond decryption sequence (Scr2n[0], Scr2n[1] . . . Scr2n[k] . . .Scr2n[m−1], Scr2n[m]) generated internally instead, so that the seconddecryption sequence is used as the basis of generating theaforementioned reception-bit conversion signal. Please note that if thephysical layer circuit 130 goes to the LPI mode, the level of thedecryption status signal (scr_status) will change (e.g. from 1 to 0) dueto some of the circuits of the physical layer circuits 130 inactive;meanwhile, the first and second decryption sequence generation circuits410, 460 will simultaneously try to establish the synchronizationseparately according to the first reception-end encryption bit (Sdn[0])and the reversed bit thereof (˜Sdn[0]) by the aforementioned means; inother words, one of the first and second decryption sequence generationcircuits 410, 460 is supposed to engage with the synchronization.

In the present embodiment, the level change of the decryption statussignal (scr_status) is based on the comparisons between thereception-end encryption bits (Sdn[0], Sdn[1], Sdn[2]) and the presetbits (Scrn[0], Scrn[1], Scrn[2]) of the first decryption sequence in apredetermined duration. If the comparison result shows that the twogroups of bits are consistent within the predetermined duration, thedecryption status signal (scr_status) indicates that the synchronizationis correct by setting its signal level (e.g. from level 0 to level 1);but if the comparison result shows that the two groups of bits fail toremain consistent within the predetermined duration, the decryptionstatus signal (scr_status) then indicates that the synchronization isincorrect by setting its signal level (e.g. from level 1 to level 0).Moreover, the predetermined duration under the LPI mode could be shorterthan that under the normal and idle modes, so as to reduce the responsetime under the LPI mode; however, this is merely exemplary, which meansthat people of ordinary skill in the art can set or adjust thepredetermined duration by their requirement or design specification.Please note that since the comparison and level change techniquesthemselves are well-known in this field, a person of ordinary skill inthe art can refer to the disclosure of the present invention to make anassembly of comparators, registers and logic gates or use a programmablelogic circuit to carry out these techniques; hence, the backgroundtechnical description is omitted here provided that the omission nowheredissatisfies the specification and enablement requirements.

Please refer to FIG. 4a , FIG. 4b and the above-description again. Thefirst decryption sequence generation circuit 410 comprises: a firstselection unit 412 (e.g. a multiplexer) for outputting the firstreception-end encryption bit (Sdn[0]) or the first preset bit (Scrn[0])according to the decryption status signal (scr_status); and a firstsequence generation unit includes a plurality of shift registers 414 andone or more calculation units 416 for producing the aforementioned firstdecryption sequence (Scrn[0], Scrn[1] . . . Scrn[k] . . . Scrn[m−1],Scrn[m]) according to the output of the first selection unit 412 inwhich the first decryption sequence is treated as the decryption basisafter locking the fore-mentioned synchronization. On the other side, thesecond decryption sequence generation circuit 460 comprises: a secondselection unit 462 (e.g. a multiplexer) for outputting the reversedfirst reception-end encryption bit (˜Sdn[0]) or the first presetoperation-bit (Scr2n[0]); and a second sequence generation unitincluding a plurality of shift registers 464 and one or more calculationunits 466 for producing the aforementioned second decryption sequence(Scr2n[0], Scr2n[1] . . . Scr2n[k] . . . Scr2n[m−1], Scr2n[m]) accordingto the output of the second selection unit 462 in which the seconddecryption sequence is treated as the decryption basis after receivingthe RX-LPI signal from the far end (i.e. reception end) and locking thesynchronization under the LPI mode. Since the selection units 412, 462,shift registers 414, 464 and calculation units 416, 466 are well-know inthis field individually, detail of these units will be omitted providedthat the disclosure and enablement requirements remain eligible.

FIG. 5 illustrates an embodiment of the operation procedure of thedecryption circuit 350 in FIG. 4a and FIG. 4b . Please refer to FIG. 5and the above description. The operation procedure comprises:

-   Step S510: using the first reception-end encryption bit (Sdn[0]) to    establish the synchronization between the encryption sequence of the    far end (a.k.a. reception end) and the decryption sequence of the    local end (a.k.a. transmission end). This step can be carried out by    the aforementioned first decryption sequence generation circuit 410    and the first decryption verification circuit 420;-   Step S520: using a first decryption sequence (Scrn[0], Scrn[1] . . .    Scrn[k] . . . Scrn[m−1], Scrn[m]) generated internally as the basis    of decryption. This step can be carried out by the first decryption    sequence generation circuit 410;-   Step S530: using the first reception-end encryption bit (Sdn[0]) to    check whether the self-generated first decryption sequence remains    synchronous with the encryption sequence. If so, go to step S540 or    else go back to step S510. This step can be carried out by the first    decryption sequence generation circuit 410 and the first decryption    verification circuit 420;-   Step S540: using the first reception-end encryption bit (Sdn[0]) and    the reversed bit thereof (˜Sdn[0]) to check whether the    self-generated first decryption sequence or a second decryption    sequence (Scr2n[0], Scr2n[1] . . . Scr2n[k] . . . Scr2n[m−1],    Scr2n[m]) remains synchronous with the encryption sequence. If not,    go to step S550 or else repeat step S540. This step can be carried    out by the aforementioned first and second decryption verification    circuits 420, 430;-   Step S550: determining whether the present mode is the LPI mode. If    so, go to step S560 or else go back to step S510;-   Step S560: verifying whether a reception signal is received    correctly. If so, go to step S570 or else repeat step S560;-   Step S570: using the first reception-end encryption bit (Sdn[0]) and    the reversed bit thereof (˜Sdn[0]) to verify the synchronization    under the LPI mode. This step can be carried out by the first and    second decryption sequence generation circuits 410, 460 and the    first and second decryption verification circuits 420, 430; and-   Step S580: using the first or second decryption sequence generated    internally as the basis of decryption, and going back to step S540.    This step can be carried out by the first decryption sequence    generation circuit 410 or the second decryption sequence generation    circuit 460.

Please note that people of ordinary skill in the art can modify any ofthe above-mentioned steps according to the disclosure of thisspecification and/or their demand or design rules with due diligence.For instance: one can add decision terms to any of the steps to therebymodify the execution timing of said step, modify parameters taken by anyof the steps to therefore adjust the execution effect of such step,ignore any of the steps if such step is unnecessary, or set newconditions to change the relation between the steps. In sum, thedecryption circuit 350 can carry out equivalent or modified stepsderived from the fore-mentioned operation procedure.

FIG. 6 illustrates an embodiment of the transmission circuit 330 and thereception circuit 340 of FIG. 3. As shown in FIG. 6, the transmissioncircuit 330 includes: a physical coding sub-layer (PCS) encoding circuit610 for generating a coded signal according to the aforementionedtransmission-end encryption signal in which the coded signal is a pulseamplitude modulation signal with three levels (PAM-3) in the presentembodiment; a physical medium attachment transmission circuit (PMA TX)620 for generating a digital transmission signal according to the codedsignal; and an analog frond end transmission circuit (AFE TX) 630 forgenerating said transmission signal according to the digitaltransmission signal, and capable of delivering the transmission signalthrough one or more pairs of transmission lines 140 with a switch (notshown). Since one of ordinary skill in the art can implement theaforementioned PCS encoding circuit 610, PMA transmission circuit 620and AFE transmission circuit 630 in light of the disclosure of thisspecification and the knowledge in this field, detail of these circuitsis omitted for succinctness provided that the disclosure and enablementrequirements remain enough. On the other side, the reception circuit 340includes: an analog front end reception circuit (AFE RX) 640 forgenerating a digital reception signal according to the aforementionedreception signal, and configured with a switch (not shown) to receivethe reception signal through one or more pairs of transmission lines 140and a digital signal processor (DSP) to handle the channel effect ofsingle or dual channels, echo, near-end crosstalk (NEXT) and far-endcrosstalk, and etc.; a physical medium attachment reception circuit (PMARX) 650 for generating a decode-awaited signal according to the digitalreception signal; and a physical coding sub-layer (PCS) decoding circuit660 for generating the aforementioned reception-end encryption signalaccording to the decode-awaited signal. Similarly, since one of ordinaryskill in the art can implement the above-mentioned AFE reception circuit640, PMA reception circuit 650 and PCS decoding circuit 660 in light ofthe disclosure of this specification and the knowledge in this field,detail of these circuits is therefore omitted.

FIG. 7a and FIG. 7b illustrate an embodiment of the operation procedureof the physical layer circuit 130 of FIG. 1. FIG. 7a shows the operationprocedure of the physical layer circuit 130 under the normal and idlemode; FIG. 7b shows the operation procedure of the physical layercircuit 130 entering the LPI mode from the idle mode. Please refer toFIG. 7a and the fore description, the operation procedure comprises:

-   Step S700: starting establishing the connection between the local    end (i.e. the transmission end, a.k.a. the network communication    device 100 of FIG. 1) and the far end (i.e. the reception end 150 of    FIG. 1);-   Step S705: establishing parameters for connection in the local end;-   Step S710: assisting the far end in establishing parameters for    connection;-   Step S715: if the reception statuses of the local and far ends are    prepared, transmitting data or an idle signal; if the reception    status of the local end is found to be ill-prepared in a waiting    duration, going back to step S705; if the reception status of the    local end is found to be prepared but the reception status of the    far end is found to be ill-prepared within the waiting duration,    going to step S720; and-   Step S720: if the reception status of the local end is prepared but    the reception status of the far end is ill-prepared, sending the    idle signal; afterwards, if the reception status of the local end    within the above-mentioned waiting duration is found to be    ill-prepared, going back to step S705; if the reception statuses of    the local and far ends are found to be prepared within the waiting    duration, going to step S715.

Please refer to FIG. 7b and the fore description. The operationprocedure further comprises:

-   Step S750: after step S715, if the reception statuses of the local    and far ends are prepared and ask for LPI mode concurrently,    updating parameters of the local end;-   Step S755: if the local end keeps asking for LPI mode for an update    time while the far end keeps asking for LPI mode or finishes    updating parameters, performing post-update preparation; if the    local end stops asking for LPI mode or the far end stops asking for    LPI mode or fails to finish updating parameters, going back to step    S715;-   Step S760: if a post-update time is complete, no signal is detected    or the far end finishes updating parameters, counting a sleep    waiting duration; if the far end fails to finish updating parameters    or stops asking for LPI mode, going back to step S715;-   Step 765: if no signal is detected within the sleep waiting    duration, entering the LPI mode and counting a sleep duration; if a    signal is detected within the sleep duration, going back to step    S705;-   Step S770: after finishing counting the sleep duration or finding    that the far or local end asks for leaving the LPI mode, counting a    transmission-end wake-up duration and a connection-failure duration;-   Step S775: after finishing counting the transmission-end wake-up    duration, rapidly establishing parameters for connection in the    local end; and-   Step S780: after finishing establishing the parameters for the local    end connection, rapidly assisting the far end in establishing    parameters for connection and going back to step S750 when the    reception statuses of the local and far ends are prepared; if    finishing counting the above-mentioned connection-failure duration    (which means that no connection is built within that duration),    going back to step S705.

Please note that the above-described operation procedures are forunderstanding, not for limiting the scope of the present invention.People of ordinary skill in the art can modify the procedure accordingto the disclosure of this specification and/or their demand or designrules with due diligence. For instance: one can add decision terms toany of the steps to thereby modify the execution timing of said step,modify parameters taken by any of the steps to therefore adjust theexecution effect of such step, eliminate any of the steps if such stepis useless, or set new conditions to change the relation between thesteps. In brief, the physical layer circuit 130 can carry out equivalentor modified steps derived from the fore-mentioned operation procedures.Please also note that steps of each of the embodiments in thisspecification are not confined to a specific execution order providedthat such steps themselves do not need the execution order.

In addition to the above-disclosed network communication device 100, thepresent invention provides an energy efficient network communicationmethod which can be carried out by the network communication device 100or the equivalent device thereof. Please refer to FIG. 8; an embodimentof the network communication method comprises the following steps:

-   Step S810: entering an idle mode from a normal mode. In this    embodiment, the normal and idle modes comply with IEEE Ethernet    network standard;-   Step S820: outputting a transmission-end low power idle indication    (i.e. TX-LPI indication);-   Step S830: generating a transmission-end low power idle signal (i.e.    TX-LPI signal) according to the TX-LPI indication;-   Step S840: converting the TX-LPI signal into a transmission signal;-   Step S850: asking a reception end to enter a low power idle mode    (i.e. LPI mode) by sending the transmission signal to the reception    end through at least one of several pairs of transmission lines, and    keeping at least another one of the several pairs of transmission    lines unused;-   Step S860: using the at least one of the several pairs of    transmission lines to receive a reception signal from the reception    end while keeping the at least another one of the several pairs of    transmission lines unused;-   Step S870: converting the reception signal into a reception-end low    power idle signal (i.e. RX-LPI signal); and-   Step S880: after outputting the transmission signal and/or receiving    the RX-LPI signal, entering the LPI mode from the idle mode, so as    to stop the operation of some circuits of the device executing the    present method for power saving, wherein the power consumption under    the normal mode is higher than that under the idle mode while the    power consumption under the idle mode is higher than that under the    LPI mode.

The above-described method can further comprises the following steps:outputting a low power idle stop indication (LPI stop indication);asking the reception end to leave the LPI mode by sending a wake-upsignal to it according to the LPI stop indication; and after issuing thewake-up signal and/or finding that the reception end itself asks forleaving the LPI mode, quitting the LPI mode.

Please note that one can find more explanation of the TX-LPI and RX-LPIsignals from the fore-disclosed embodiments. Besides, in theabove-mentioned steps, the step of converting the TX-LPI signal into thetransmission signal includes: generating a transmission-bit conversionsignal according to the TX-LPI signal in which the bit number of theTX-LPI signal is different from the bit number of the transmission-bitconversion signal; generating a transmission-end encryption signalaccording to the transmission-bit conversion signal; and generating thetransmission signal according to the transmission-end encryption signal.On the other side, the step of converting the reception signal into theRX-LPI signal includes: generating a reception-end encryption signalaccording to the reception signal; generating a reception-bit conversionsignal according to the reception-end encryption signal; and generatingthe RX-LPI signal according to the reception-bit conversion signal whosebit number is different from the bit number of the RX-LPI signal.Moreover, the step of generating the transmission-end encryption signalincludes: generating a plurality of transmission-end encryption bitsaccording to the transmission-bit conversion signal; and performing alogic operation with at least some of the transmission-end encryptionbits to thereby generate the transmission-end encryption signal, whereinan example of the logic operation is an Exclusive-OR operation.Furthermore, the step of generating the reception-bit conversion signalincludes: generating a plurality of reception-end encryption bitsaccording to the reception-end encryption signal; and performing acomparison operation with at least some of the reception-end encryptionbits to thereby generate the reception-bit conversion signal. As to thestep of outputting the TX-LPI indication, it can include: outputting theTX-LPI indication in light of a buffer capacity threshold.

Since one of ordinary skill in the art can appreciate detail andmodification of this method invention by referring to the fore-discloseddevice invention, redundant and unnecessary description is thereforeomitted.

To sum up, the energy efficient network communication device and methodare capable of utilizing some of several pairs of transmission lines(e.g. one or two pairs among four pairs of transmission lines) fortransmission and reception when keeping the others of the several pairsof transmission lines (e.g. the other three or two pairs among the fourpairs of transmission lines) unused, and capable of entering the LPImode under an appropriate condition for power saving. Besides, thepresent invention uses undefined parameters combination (e.g. thecombination of the aforementioned transmission bits) in comparison withthe prior art and a simple logic operation (e.g. an Exclusive-ORoperation) for carrying the information of the LPI mode, and uses acomparison operation (e.g. an inversion operation plus a comparisonoperation) to determine whether a received signal contains theinformation of the LPI mode, so that the power saving effect can berealized without changing the circuit design and connection proceduresignificantly. Furthermore, by installing the aforementionedtransmission buffer to provide the TX-LPI indication, the presentinvention can make use of a media access control circuit in compliancewith 100 BASE-T which can not issue the TX-LPI indication on its own,and thereby simplifies the whole design.

The aforementioned descriptions represent merely the preferredembodiment of the present invention, without any intention to limit thescope of the present invention thereto. Various equivalent changes,alterations, or modifications based on the claims of present inventionare all consequently viewed as being embraced by the scope of thepresent invention.

What is claimed is:
 1. An energy efficient network communication device,comprising: a media access controller for outputting a transmission-endlow power idle indication (TX-LPI indication) and receiving areception-end low power idle indication (RX-LPI indication), including:a media access control circuit coupled to a media independent receptioninterface; and a transmission buffer, coupled between the media accesscontrol circuit and a media independent transmission interface, foroutputting the TX-LPI indication according to a buffer capacitythreshold after the media access control circuit stops sending packets;a media independent interface including: the media independenttransmission interface for generating a transmission-end low power idlesignal (TX-LPI signal) according to the TX-LPI indication; and the mediaindependent reception interface for generating the RX-LPI indicationaccording to a reception-end low power idle signal (RX-LPI signal); anda physical layer circuit, electrically coupled to the media independentinterface and several pairs of transmission lines, including: a physicallayer transmission circuit, coupled to the media independenttransmission interface, for converting the TX-LPI signal into atransmission signal and sending the transmission signal to a receptionend to ask the reception end to enter a low power idle mode (LPI mode);and a physical layer reception circuit, coupled to the media independentreception interface, for receiving a reception signal from the receptionend and converting the reception signal into the RX-LPI signal, whereinthe physical layer circuit uses at least one of the several pairs oftransmission lines to send the transmission signal and receive thereception signal, and keeps at least another one of the several pairs oftransmission lines unused, and after sending the transmission signaland/or receiving the RX-LPI signal, the physical layer circuit entersthe LPI mode from an idle mode and stops the operation of some or all ofthe physical layer circuit to reduce power consumption.
 2. The energyefficient network communication device of claim 1, wherein the TX-LPIsignal includes a first transmission bit, a second transmission bit anda third transmission bit in which the first transmission bit has a firstpredetermined value, the second transmission bit has a secondpredetermined value and the third transmission bit has a thirdpredetermined value, and the RX-LPI signal includes a first receptionbit, a second reception bit and a third reception bit in which the firstreception bit corresponds to the first predetermined value, the secondreception bit corresponds to the second predetermined value and thethird reception bit corresponds to the third predetermined value.
 3. Theenergy efficient network communication device of claim 1, wherein thephysical layer transmission circuit includes: a transmission-bitconversion circuit, coupled to the media independent transmissioninterface, for generating a transmission-bit conversion signal accordingto the TX-LPI signal in which the bit number of the TX-LPI signal isdifferent from the bit number of the transmission-bit conversion signal;an encryption circuit, coupled to the transmission-bit conversioncircuit, for generating a transmission-end encryption signal accordingto the transmission-bit conversion signal; and a transmission circuit,electrically coupled to the several pairs of transmission lines, forgenerating the transmission signal according to the transmission-endencryption signal.
 4. The energy efficient network communication deviceof claim 3, wherein the encryption circuit generates a plurality oftransmission-end encryption bits according to the transmission-bitconversion signal, and performs a logic operation with at least some ofthe transmission-end encryption bits to thereby generate thetransmission-end encryption signal.
 5. The energy efficient networkcommunication device of claim 4, wherein the plurality oftransmission-end encryption bits includes a first transmission-endencryption bit, a second transmission-end encryption bit and a thirdtransmission-end encryption bit in which the first transmission-endencryption bit represents the TX-LPI indication, the secondtransmission-end encryption bit represents a transmission-endupdate-completion indication and the third transmission-end encryptionbit represents a transmission-end reception status.
 6. The energyefficient network communication device of claim 4, wherein the logicoperation is an Exclusive-OR operation.
 7. The energy efficient networkcommunication device of claim 3, wherein the transmission circuitincludes: a physical coding sub-layer encoding circuit for generating acoded signal in accordance with the transmission-end encryption signal;a physical medium attachment transmission circuit for generating adigital transmission signal according to the coded signal; and an analogfront end transmission circuit for generating the transmission signalaccording to the digital transmission signal.
 8. The energy efficientnetwork communication device of claim 1, wherein the physical layerreception circuit includes: a reception circuit, electrically connectedto the several pairs of transmission lines, for generating areception-end encryption signal according to the reception signal; adecryption circuit, coupled to the reception circuit, for generating areception-bit conversion signal according to the reception-endencryption signal; and a reception-bit conversion circuit, coupled tothe decryption circuit and the medium independent reception interface,for generating the RX-LPI signal according to the reception-bitconversion signal in which the bit number of the RX-LPI signal isdifferent from the bit number of the reception-bit conversion signal. 9.The energy efficient network communication device of claim 8, whereinthe decryption circuit includes: a first decryption sequence generationcircuit for providing a first decryption sequence according to thereception-end encryption signal in which the first decryption sequenceis used as the basis of generating the reception-bit conversion signaland includes a first preset bit; a first decryption verification circuitfor generating a decryption verification signal according to a firstreception-end encryption bit of the reception-end encryption signal andthe first preset bit; a second decryption verification circuit forgenerating the decryption verification signal according to the reversedbit of the first reception-end encryption bit and a first presetoperation-bit; and a second decryption sequence generation circuit forproviding a second decryption sequence as the basis of generating thereception-bit conversion signal in which the second decryption sequenceincludes the first preset operation-bit.
 10. The energy efficientnetwork communication device of claim 8, wherein the decryption circuitgenerates a plurality of reception-end encryption bits and performs acomparison operation with at least some of the plurality ofreception-end encryption bits to thereby generate the reception-bitconversion signal.
 11. The energy efficient network communication deviceof claim 10, wherein the decryption circuit checks whether a decryptionsequence of the decryption circuit is synchronous with an encryptionsequence of the reception end by the comparison operation, anddetermines whether the reception end asks for the low power idle mode.12. The energy efficient network communication device of claim 8,wherein the reception circuit includes: an analog front end receptioncircuit for generating a digital reception signal according to thereception signal; a physical medium attachment reception circuit forgenerating a decode-awaited signal according to the digital receptionsignal; and a physical coding sub-layer decoding circuit for generatingthe reception-end encryption signal according to the decode-awaitedsignal.
 13. The energy efficient network communication device of claim1, wherein if the media access controller is going to send packets, itsends a low power idle stop indication (LPI stop indication) to thephysical layer circuit; and the physical layer circuit asks thereception end to leave the LPI mode by sending a wake-up signal to thereception end according to the LPI stop indication, and leaves the LPImode after receiving the LPI stop indication and/or ascertaining thatthe reception end asks for leaving the LPI mode.
 14. The energyefficient network communication device of claim 1, wherein thetransmission buffer includes: a storage unit for storingdelivery-awaited packets; a buffer capacity monitoring unit for watchingthe capacity of the storage unit according to the buffer capacitythreshold, and issuing a notification signal if the capacity of thestorage unit reaches the buffer capacity threshold; and a low power idleindication generation unit for sending the TX-LPI indication accordingto the notification signal.
 15. The energy efficient networkcommunication device of claim 14, wherein after the media access controlcircuit starts sending packets, the transmission buffer outputting a lowpower idle stop indication (LPI stop indication) to the physical layercircuit through the media independent transmission interface inaccordance with the buffer capacity threshold; and the physical layercircuit asks the reception end to leave the LPI mode by sending awake-up signal according to the LPI stop indication, and quits the LPImode after receiving the LPI stop indication and/or ascertaining thatthe reception end asks for leaving the LPI mode.
 16. The energyefficient network communication device of claim 1, which enters the idlemode from a normal mode before sending the LPI indication, wherein thepower consumption under the normal mode is higher than the powerconsumption under the idle mode while the power consumption under theidle mode is higher than the power consumption under the LPI mode. 17.An energy efficient network communication method, which is carried outby an energy efficient network communication device, comprising:entering an idle mode from a normal mode; generating a transmission-endlower power idle indication (TX-LPI indication); generating atransmission-end lower power idle signal (TX-LPI signal) according tothe TX-LPI indication; converting the TX-LPI signal into a transmissionsignal with at least the following sub-steps: generating atransmission-bit conversion signal according to the TX-LPI signal inwhich the bit number of the TX-LPI signal is different from the bitnumber of the transmission-bit conversion signal; generating a pluralityof transmission-end encryption bits according to the transmission-bitconversion signal and performing a logic operation with at least some ofthe transmission-end encryption bits to generate a transmission-endencryption signal; and generating the transmission signal according tothe transmission-end encryption signal; using at least one of severalpairs of transmission lines to output the transmission signal to areception end for asking the reception end to enter a lower power idlemode (LPI mode) when keeping at least another one of the several pairsof transmission lines unused; using the at least one of the severalpairs of transmission lines to receive a reception signal from thereception end when keeping the at least another one of the several pairsof transmission lines unused; converting the reception signal into areception-end low power idle signal (RX-LPI signal) with at least thefollowing sub-steps: generating a reception-end encryption signalaccording to the reception signal; generating a plurality ofreception-end encryption bits according to the reception-end encryptionsignal and performing a comparison operation with at least some of thereception-end encryption bits to generate a reception-bit conversionsignal; and generating the RX-LPI signal according to the reception-bitconversion signal in which the bit number of the RX-LPI signal isdifferent from the bit number of the reception-bit conversion signal;and after outputting the transmission signal and/or receiving the RX-LPIsignal, entering the LPI mode from the idle mode for power saving,wherein the power consumption under the normal mode is higher than thepower consumption under the idle mode while the power consumption underthe idle mode is higher than the power consumption under the LPI mode.18. The energy efficient network communication method of claim 17,wherein the TX-LPI signal includes a first transmission bit, a secondtransmission bit and a third transmission bit in which the first, secondand third transmission bits respectively have a first predeterminedvalue, a second predetermined value and a third predetermined value; andthe RX-LPI signal includes a first reception bit, a second reception bitand a third reception bit in which the first, second and third receptionbits respectively correspond to the first, second and thirdpredetermined values.
 19. The energy efficient network communicationmethod of claim 17, wherein the logic operation is an Exclusive-ORoperation.
 20. The energy efficient network communication method ofclaim 17, further comprising: generating a low power idle stopindication (LPI stop indication); asking the reception end to leave theLPI mode by sending a wake-up signal according to the LPI stopindication; and leaving the LPI mode in accordance with the LPI stopindication and/or a signal from the reception end asking for leaving theLPI mode.
 21. The energy efficient network communication method of claim17, wherein the step of generating the TX-LPI indication includes:generating the TX-LPI indication according to a buffer capacitythreshold.